.alpha..sub.1 -Adrenergic receptors (.alpha..sub.1 -adrenoceptocs) mediate the contractile state of smooth muscle tissue. For example, hypersympathetic activity produces contraction of vascular smooth muscle which -Leads to elevated blood pressures. Thus, .alpha..sub.1 -adrenoceptor antagonists find use as anti-hypertensive agents. .alpha..sub.1 -Adrenoceptor stimulation also produces contraction of urethral and bladder neck smooth muscle, leading to increased resistance in urinary outflow. Thus, .alpha..sub.1 -adrenoceptor antagonists are useful in treating conditions which relate directly or indirectly to obstructive uropathies, particularly obstruction due to benign prostatic hyperplasia (BPH) (Lepor, H. The Prostate Supplement 1990, 3, 75-84). However, the amount of .alpha..sub.1 -adrenoceptor antagonist required to produce a therapeutic effect with regard to urinary outflow, can produce an excessive decrease of blood pressure and/or an inhibition of the mechanism by which normal blood pressure is maintained during changes in posture (i.e., postural hypotension). Thus, antagonists which can selectively reduce .alpha..sub.1 -adrenoceptor hyperactivity in prostatic and/or lower urinary tract smooth muscle, without affecting blood pressure or causing postural hypotension, are desirable.
The disclosures of these and other documents referred to throughout this application (e.g., in the Pharmacology section of the Detailed Description of the Invention) are incorporated herein by reference.